image/png: don't silently swallow io.ReadFull's io.EOF error when it

lands exactly on an IDAT row boundary.

Fixes #10493

Change-Id: I12be7c5bdcde7032e17ed1d4400db5f17c72bc87
Reviewed-on: https://go-review.googlesource.com/9270
Reviewed-by: Rob Pike <r@golang.org>

diff --git a/src/image/png/reader.go b/src/image/png/reader.go
index dae7a7db37df44f2920fcb0ef70b5b94676400fe..33218e15160ae0a09d1ebf84a1907f2dd8ea962c 100644 (file)
--- a/src/image/png/reader.go
+++ b/src/image/png/reader.go
@@ -326,9 +326,15 @@ func (d *decoder) decode() (image.Image, error) {
        var img image.Image
        if d.interlace == itNone {
                img, err = d.readImagePass(r, 0, false)
+               if err != nil {
+                       return nil, err
+               }
        } else if d.interlace == itAdam7 {
                // Allocate a blank image of the full size.
                img, err = d.readImagePass(nil, 0, true)
+               if err != nil {
+                       return nil, err
+               }
                for pass := 0; pass < 7; pass++ {
                        imagePass, err := d.readImagePass(r, pass, false)
                        if err != nil {
@@ -430,6 +436,9 @@ func (d *decoder) readImagePass(r io.Reader, pass int, allocateOnly bool) (image
                // Read the decompressed bytes.
                _, err := io.ReadFull(r, cr)
                if err != nil {
+                       if err == io.EOF || err == io.ErrUnexpectedEOF {
+                               return nil, FormatError("not enough pixel data")
+                       }
                        return nil, err
                }
 

diff --git a/src/image/png/reader_test.go b/src/image/png/reader_test.go
index 9f24f041e56ddd59bd4d18595eae56b2bce8e1ca..1f92f8c221b96018691abe23ece7772fd71c9cc6 100644 (file)
--- a/src/image/png/reader_test.go
+++ b/src/image/png/reader_test.go
@@ -320,6 +320,21 @@ func TestPalettedDecodeConfig(t *testing.T) {
        }
 }
 
+func TestIncompleteIDATOnRowBoundary(t *testing.T) {
+       // The following is an invalid 1x2 grayscale PNG image. The header is OK,
+       // but the zlib-compressed IDAT payload contains two bytes "\x02\x00",
+       // which is only one row of data (the leading "\x02" is a row filter).
+       const (
+               ihdr = "\x00\x00\x00\x0dIHDR\x00\x00\x00\x01\x00\x00\x00\x02\x08\x00\x00\x00\x00\xbc\xea\xe9\xfb"
+               idat = "\x00\x00\x00\x0eIDAT\x78\x9c\x62\x62\x00\x04\x00\x00\xff\xff\x00\x06\x00\x03\xfa\xd0\x59\xae"
+               iend = "\x00\x00\x00\x00IEND\xae\x42\x60\x82"
+       )
+       _, err := Decode(strings.NewReader(pngHeader + ihdr + idat + iend))
+       if err == nil {
+               t.Fatal("got nil error, want non-nil")
+       }
+}
+
 func TestMultipletRNSChunks(t *testing.T) {
        /*
                The following is a valid 1x1 paletted PNG image with a 1-element palette